Daniel Sank Updated 2025-07-16
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Started at Google Quantum AI in 2014.
Has his LaTeX notes at: github.com/DanielSank/theory. One day he will convert to OurBigBook.com. Interesting to see that he is able to continue his notes despite being at Google.
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Sycamore processor Updated 2025-07-16
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This is a good read: quantumai.google/hardware/datasheet/weber.pdf May 14, 2021. Their topology is so weird, not just a rectangle, one wonders why! You get different error rates in different qubits, it's mad.
Figure 1.
Google Sycamore Weber quantum computer connectivity graph
. Weber is a specific processor of the Sycamore family. From this we see it clearly that qubits are connected to at most 4 other qubits, and that the full topology is not just a simple rectangle.
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Who are the developers that are making the most money through GitHub sponsors? Updated 2025-07-16
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Inside Job (2010) Updated 2025-07-16
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Margin Call (2011) Updated 2025-07-16
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Video 1.
Peter Sullivan discovers the issue scene from Margin Call
. Source.
Video 2.
Senior partners emergency meeting scene from Margin Call
. Source. God, Jeremy Irons is destroying it!!! And all others too.
Video 3.
Fire Sale of Mortgage Bonds scene from Margin Call
. Source.
Video 4.
Investment Analyst Explains Margin Call by The Plain Bagel
. Source.
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The Big Short (2015) Updated 2025-07-16
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Video 1.
I'm Jacked to the Tits remix by The Big Short (2021)
Source.
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FeatherJS demo apps Updated 2025-07-16
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FeathersJS Heroku deployment Updated 2025-07-16
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One major step was to port to PostgreSQL as shown at feathers-chat PostgreSQL.
There's also a heroku branch at: github.com/feathersjs/feathers-chat/tree/heroku, but it also seems to use NeDB? So you can have a filesystem in Heroku? Doesn't seem so: stackoverflow.com/questions/42775418/heroku-local-persistent-storage
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FeathersJS signup email verification Updated 2025-07-16
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Faster-than-light implies time travel Updated 2025-07-16
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Figure 1.
Spacetime diagram illustrating how faster-than-light travel implies time travel
. Legend an explanation are shown in this answer.
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Tachyon Updated 2025-07-16
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Tachyonic antitelephone Updated 2025-07-16
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Realworld app written in Express Updated 2025-07-16
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gothinkster/realworld implementations based on Express.js.
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ELF Hello World Tutorial / STT_FILE Updated 2025-07-16
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Entry 1 has ELF64_R_TYPE == STT_FILE. ELF64_R_TYPE is continued inside of st_info.
  • 10 8: st_name = 01000000 = character 1 in the .strtab, which until the following \0 makes hello_world.asm
    This piece of information file may be used by the linker to decide on which segment sections go: e.g. in ld linker script we write:
    segment_name :
{
    file(section)
}
    to pick a section from a given file.
    Most of the time however, we will just dump all sections with a given name together with:
    segment_name :
{
    *(section)
}
  • 10 12: st_info = 04
    Bits 0-3 = ELF64_R_TYPE = Type = 4 = STT_FILE: the main purpose of this entry is to use st_name to indicate the name of the file which generated this object file.
    Bits 4-7 = ELF64_ST_BIND = Binding = 0 = STB_LOCAL. Required value for STT_FILE.
  • 10 13: st_shndx = Symbol Table Section header Index = f1ff = SHN_ABS. Required for STT_FILE.
  • 20 0: st_value = 8x 00: required for value for STT_FILE
  • 20 8: st_size = 8x 00: no allocated size
Now from the readelf, we interpret the others quickly.
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ELF Hello World Tutorial / STT_SECTION Updated 2025-07-16
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There are two such entries, one pointing to .data and the other to .text (section indexes 1 and 2).
Num:    Value          Size Type    Bind   Vis      Ndx Name
  2: 0000000000000000     0 SECTION LOCAL  DEFAULT    1
  3: 0000000000000000     0 SECTION LOCAL  DEFAULT    2
TODO what is their purpose?
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ELF Hello World Tutorial / STT_NOTYPE Updated 2025-07-16
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Then come the most important symbols:
Num:    Value          Size Type    Bind   Vis      Ndx Name
  4: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT    1 hello_world
  5: 000000000000000d     0 NOTYPE  LOCAL  DEFAULT  ABS hello_world_len
  6: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT    2 _start
hello_world string is in the .data section (index 1). It's value is 0: it points to the first byte of that section.
_start is marked with GLOBAL visibility since we wrote:
global _start
in NASM. This is necessary since it must be seen as the entry point. Unlike in C, by default NASM labels are local.
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ELF Hello World Tutorial / SHT_SYMTAB on the executable Updated 2025-07-16
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By default, NASM places a .symtab on the executable as well.
This is only used for debugging. Without the symbols, we are completely blind, and must reverse engineer everything.
You can strip it with objcopy, and the executable will still run. Such executables are called "stripped executables".
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ELF Hello World Tutorial / .rel.text Updated 2025-07-16
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Besides sh_type == SHT_RELA, there also exists SHT_REL, which would have section name .text.rel (not present in this object file).
Those represent the same struct, but without the addend, e.g.:
typedef struct {
    Elf64_Addr  r_offset;
    Elf64_Xword r_info;
} Elf64_Rela;
The ELF standard says that in many cases the both can be used, and it is just a matter of convenience.
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ELF Hello World Tutorial / SHT_NULL Updated 2025-07-16
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In index 0, SHT_NULL is mandatory. Are there any other uses for it: stackoverflow.com/questions/26812142/what-is-the-use-of-the-sht-null-section-in-elf ?
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ELF Hello World Tutorial / PT_INTERP Updated 2025-07-16
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Contains the path to the dynamic loader, i.e. /lib64/ld-linux-x86-64.so.2 in Ubuntu 18.10. Explained at: stackoverflow.com/questions/8040631/checking-if-a-binary-compiled-with-static/55664341#55664341
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